1. Field of the Invention
This invention is concerned with catalytic reforming of gasoline feedstocks under elevated temperature and pressure. The traditional feedstocks of gasoline that may be reformed through this invention include straight run gasoline, gasoline and naphthas derived from catalytic or hydrocracking processes.
2. Background of the Prior Art
Catalytic reforming is one of the most important processes for the production of automobile fuels, particularly in light of the need for such fuels to exhibit increasing resistance to knocking, in order to meet the rising demands of high performance internal combustion engines which are currently being produced.
In the catalytic reforming process practiced under elevated pressure and temperature, a number of chemical reactions take place, including the dehydrogenation of naphthenes to aromatics, the isomerization of paraffins and naphthenes, and the dehydrocyclization of paraffins. Through hydrocracking, longer hydrocarbons are split into hydrocarbons of shorter molecular length, shorter molecule paraffins forming by the addition of hydrogen on the base olefinic particles. Due to these reactions, there is a net production of hydrogen as well as C.sub.1 to C.sub.4 hydrocarbon compounds. These reactions, taken cumulatively, lead to the increase in the resistance to knocking desired in the derived, reformed gasoline, which of course is characterized quantatively by octane rating indications. The knock strength of the fuel is measured under standardized conditions in test motors either by the motor method or the research method, both well known prior art methods and generally indicated as MOR (motor octane rating) or ROR (research octane rating).
The octane rating for n-heptane is by definition 0, that of iso-octane 100. Octane ratings of more than 100 are achieved by the addition of tetraethyl lead to iso-octane.
In view of environmental and pollution concerns, as well as modifications in the design and operation of internal combustion engines, it is desirable to limit to the greatest possible degree the addition of lead compounds as a method of raising the knock resistance of gasoline fuels, so that there continues to exist a demand for light fuels with extremely high knock resistance, in the absence of added lead compounds.
Accordingly, it is one object of the invention to provide a gasoline fuel of increased knock resistance or octane rating, in the absence of added lead compounds.
It is another object of this invention to limit the formation of C.sub.1 -C.sub.4 hydrocarbon gases during the catalytic reforming process, to avoid the considerable loss of carbon occurring therefrom.
It is another object of this invention to provide a process which uses conventional catalytic reforming process parameters and apparatus, and yet provides an increased yield of desirable fluid products (C.sub.5 + hydrocarbons) along with improved values of knock resistance in gasolines designed for use as automobile fuels. With respect to the state of the art of conventional catalytic reforming, used feedstocks and applied process parameters, it is referred, for example to Hydrocarbon Processing, Sept. 1980, p. 162.